Comparison of adjuvant activities of aluminium phosphate, calcium phosphate and stearyl tyrosine for tetanus toxoid.

The adjuvant activity of three adjuvants, aluminium phosphate (AIPO4), calcium phosphate (CaHPO4) and stearyl tyrosine for tetanus toxoid (TT) were compared to soluble TT in mice at a dose of 0.5 Lf (1/10th of the single human dose) and in guinea-pigs at a dose of 7.5 Lf (1.5 times the single human dose). Three TT preparations varying in purity were used: (1) ammonium sulphate precipitated formalin detoxified tetanus toxin (AS-TT); (2) AS-TT ultrafiltered to remove low molecular weight peptides (UF-TT): and (3) chromatographically purified tetanus toxin subsequently detoxified with formalin (CP-TT). After primary immunization of mice, AIPO4 absorbed TTs induced higher toxin-neutralizing and IgG (by ELISA) antibodies than CaHPO4, stearyl tyrosine adsorbed or soluble TT preparations, but this difference was no longer present after secondary immunization. TT preparations of varying purities showed similar antibody responses after primary and secondary immunizations when adsorbed on each adjuvant. CP-TT preparation showed the highest neutralizing antibody level amongst soluble preparations after the first dose. All the preparations induced mainly IgG1 antibodies. However, stearyl tyrosine adsorbed TT induced relatively higher IgG2a and IgG2b responses than AIPO4, CaHPO4 adsorbed or soluble TTs particularly after booster injection. No preparation induced detectable IgG3 or IgM antibodies. AIPO4 adsorbed preparations induced higher IgE antibodies than CaHPO4 and stearyl tyrosine adsorbed vaccines. Among the soluble preparations, CP-TT induced lower anti-TT IgE antibodies than standard AS-TT. All these preparations were also tested in the US potency test for adsorbed TT in guinea-pigs. While all the preparations passed this test, AIPO4 adsorbed TT preparations induced higher neutralizing and IgG antibodies than CaHPO4 and stearyl tyrosine adsorbed or soluble TT preparations. In these animal models, purified TT was a strong immunogen and traditional AIPO4 adjuvant gave the highest antibody responses.